使用 HealthKit 的后台交付检索步骤后，在后台将数据写入 Firebase

Question

我有一个HKObserverQuery在后台获取步骤的设置（enableBackgroundDelivery方法在 中调用application:didFinishLaunchingWithOptions:）。

这些步骤是在后台检索的，但我也想将检索到的步骤存储在 Firebase 数据库中。不过，这部分失败了，Firebase 中没有存储任何内容。当应用程序在前台时，存储步骤的方法确实可以正常工作。任何有关如何在后台成功在 Firebase 中写入数据的想法都将不胜感激。

class HealthKitManager {

    static let shared = HealthKitManager()
    private let healthStore = HKHealthStore()
    private let stepsQuantityType = HKQuantityType.quantityType(forIdentifier: .stepCount)!

    private init() {

    }

    func getTodaysStepCount(completion: @escaping (Double) -> Void) {
        let now = Date()
        let startOfDay = Calendar.current.startOfDay(for: now)
        let predicate = HKQuery.predicateForSamples(withStart: startOfDay, end: now, options: .strictStartDate)

        let query = HKStatisticsQuery(quantityType: stepsQuantityType, quantitySamplePredicate: predicate, options: .cumulativeSum) { (_, result, error) in
            var resultCount = 0.0

            guard let result = result else {
                log.error("Failed to fetch steps = \(error?.localizedDescription ?? "N/A")")
                completion(resultCount)
                return
            }

            if let sum = result.sumQuantity() {
                resultCount = sum.doubleValue(for: HKUnit.count())
            }

            DispatchQueue.main.async {
                completion(resultCount)
            }
        }

        healthStore.execute(query)
    }

    func enableBackgroundDelivery() {
        let query = HKObserverQuery(sampleType: stepsQuantityType, predicate: nil) { [weak self] (query, completionHandler, error) in
            if let error = error {
                log.error("Observer query failed = \(error.localizedDescription)")
                return
            }

            self?.getTodaysStepCount(completion: { steps in
                // Store steps using Firebase:
                StepsManager.shared.updateUserSteps(steps)
                completionHandler()
            })
        }

        healthStore.execute(query)
        healthStore.enableBackgroundDelivery(for: stepsQuantityType, frequency: .hourly) { (success, error) in
            log.debug("Background delivery of steps. Success = \(success)")

            if let error = error {
                log.error("Background delivery of steps failed = \(error.localizedDescription)")
            }
        }
    }

}

Answer 1

好的，我解决了这个问题。问题是我正在调用 completionHandler，告诉 HealthKit 我的操作已经完成，然后才真正完成了保存到 Firebase 的操作。保存到 Firebase 是异步完成的。

我添加了一个完成处理程序来StepsManager.shared.updateUserSteps运行：

func updateUserSteps(_ steps: Double, completion: (() -> Void)? = nil) {
    let stepsReference = databaseInstance.reference(withPath: stepsPath)
    stepsReference.setValue(steps) { _, _ in
        completion?()
    }
}

databaseRef.setValue完成时触发。然后我将观察者查询更新为以下内容：

self?.getTodaysStepCount(completion: { steps in
    StepsManager.shared.updateUserSteps(steps) {
        completionHandler() // the HKObserverQueryCompletionHandler
    }
})

Firebase 操作现在正确完成。